The present invention concerns a door that can be opened and closed by raising and lowering it vertically, that can be installed against a ceiling and slide up and down on rollers, or that can be tilted or swung up and down. It features a weight-compensation mechanism attached to it at one end and to a fixed point at the other and including one or more helical-spring modules.
Equipping overhead doors with weight-compensation means to maintain the forces need to open and close them weak is known. Such means include "torsion" springs that apply forces to the door by means of cords and weight-compensation shafts and helical springs, both tension and compression.
When helical springs are involved, means of preventing broken sections from flinging out are necessary. Such means can be tubes that telescope in the event of breakage and devices that extend within the spring and intercept the fragments.
The diameter of the tubes must be longer, the longer the diameter of the spring, which depends in turn on its performance curve in that springs intended to accommodate more powerful forces must be wider than those intended to accommodate weaker ones.
Several weak helical tension springs have been paralleled as an alternative to a single more powerful spring. In this approach, however, each individual spring must be provided with a safety-ensuring device of its own extending through it.
The advantage of several parallel springs is that, if a spring breaks, the forces acting on the door will not all be eliminated. Still, a module comprising several springs of specific power or storage capacity will occupy considerable space.